$\lim_{x\to-\infty}\left(\frac{\left(x^6-23\right)}{x-9}\right)$

$exp\left(2y\right)\cdot\left(x^2+1\right)^2\frac{dy}{dx}=-x$

$x^2-9x^2yz+zxy-2yz-32xyz$

$\int\frac{1}{x^3\left(x+4\right)^2}dx$

$\left(y^2+xy^2\right)\frac{dy}{dx}+x-xy^2=0$

$\left(x-2y\right)dx+\left(4x-3y\right)dy=0$

$\frac{7}{a}-\frac{3}{a}$